The object of this invention is new compounds capable of modulating the activity of nuclear LXR receptors, a method of producing these and pharmaceutical compounds containing them.
Liver X receptors (LXR) are transcription factors belonging to the super family of nuclear receptors to which retinoic acid receptors (RXR), farnesoid X receptors (FXR) and peroxisome proliferator-activated receptors (PPARs) also belong. LXR receptors form, by linking to the RXR receptor, a heterodimer which bonds in a specific manner to the ADN response elements (LXRE) leading to the transactivation of target genes (Genes dev. 1995; 9: 1033-45).
These receptors are involved in a number of metabolic routes and are in particular involved in the homeostasis of cholesterol, bile acids, triglycerides and glucose.
Modulation of the activity of these nuclear receptors affects the progression of metabolic disorders such as Type II diabetes, dyslipidemias and the development of atherosclerosis.
The LXR/RXR heterodimer can be activated by LXR and/or RXR ligands. The transactivation of the target genes calls for the recruitment of co-activators such as Grip-1. (Nature 1996; 383: 728-31).
The two types of LXR receptors identified today, namely LXRα and LXRβ, have a high degree of similarity in terms of their amino acid sequence but differ in terms of their tissular distribution. LXRα is strongly expressed in the liver and to a lesser extent in the kidneys, the intestine, the adipose tissue and the spleen. LXRβ is distributed in a ubiquitous manner (Gene 2000; 243: 93-103, N.Y. Acad. Sci. 1995; 761: 38-49).
Although cholesterol does not directly activate the LXR receptors, mono-oxygenated derivatives of cholesterol (oxysterols) do, and more specifically 22(R)-hydroxycholesterol, 24(S)-hydroxycholesterol and 24(S),25-epoxycholesterol. These oxysterols are considered to be the physiological ligands of the LXR receptors (Nature 1996; 383: 728-31, J. Biol. chem 1997; 272: 3137-40). Furthermore, it has been shown that oxysterol 5,6,24(S),25-diepoxycholesterol is a specific ligand of LXRα, suggesting that it is possible to develop specific ligands of LXRα and/or LXRβ (Proc. Natl. Acad. Sci USA 1999; 96: 26-71, Endocrinology 2000; 141: 4180-4).
Furthermore, it has been possible to show that human plasma contains natural LXRα and β antagonists (Steroïds 2001; 66: 473-479).
Using the hepatocytes of rats, it has been possible to show that unsaturated fatty acids significantly increase the expression of LXRα without affecting LXRβ (Mol Endocrinol 2000; 14:161-171). Moreover, the α and γ PPARs activators also induce the expression of LXRα in the human primary macrophages.
The strong concentrations of LXRα in the liver and the identification of the endogenous ligands of LXR have suggested that these receptors play an essential role in cholesterol metabolism. Under physiological conditions, the homeostasis of cholesterol is maintained through regulation of the novo synthesis and catabolism channels. The accumulation of sterols in the liver leads via a feedback mechanism involving transcription factors such as SREBP-1 and SREBP-2 to the inhibition of cholesterol biosynthesis. (Cell 1997; 89: 331-40). The excess cholesterol also activates another metabolic route which leads to the conversion of cholesterol into bile acids. The conversion of cholesterol into 7α-hydroxy-cholesterol is performed by a localised enzyme in the liver (CYP7A: 7α-hydroxylase) (J. Biol. Chem. 1997; 272: 3137-40).
The involvement of LXR in the synthesis of bile acids and therefore in the regulation of cholesterol homeostasis has been demonstrated using LXRα deficient mice which, when subjected to a fat-rich diet, accumulate large quantities of cholesterol esters at the hepatic level (Cell 1998; 93 693-704). The LXRβ deficient mice have the same physiological resistance as the normal mice to a fat-enriched diet. The unchanged expression of the LXRβ in the LXR deficient mice tends to demonstrate that LXRβ is incapable on its own of significantly increasing cholesterol metabolism (J. Clin. Invest. 2001; 107: 565-573).
The LXR receptors expressed at the macrophage level play an important role in the regulation of certain functions of this. More specifically, they are involved in control of the inverse transport of cholesterol which allows export of excess cholesterol from the peripheral tissues towards the liver. The cholesterol is taken up by the pre-bHDL via the apoA1 and ABCA1 in order to be transported to the liver where it is catabolised into bile acids and then eliminated.
ABCA1 is a member of the super family of transport proteins (ATP-binding cassette) the importance of which is illustrated by the fact that a mutation at gene level of the ABCA1 is responsible for Tangier disease (Nat. Genet. 1999; 22: 336-45).
The expression of ABCA1 and the efflux of cholesterol are induced by the loading of the human macrophages with cholesterol and the activation of the LXR receptors (Biochem. Biophys. Res. Comm. 1999; 257: 29-33). It was also subsequently shown that the expression at the intestinal level of ABCG1, ABCG5 and ABCG8, other members of the ABC type transporters family, is also regulated by the RXR/LXR heterodimer (J. Biol. Chem. 2000; 275: 14700-14707, Proc. Natl. Acad. Sci. USA 2000; 97: 817-22, J. Biol. Chem. 2002; 277: 18793-18800, Proc. Natl. Acad. Sci. USA 2002; 99: 16237-16242).
It was also shown that LXR agonist ligands reduced atheromatous lesions in two different murine models (ApoE−/− mouse and LDLR−/− mouse) (Proc. Natl. Acad. Sci. USA 2002; 99:7604-7609, FEBS Letters 2003; 536: 6-11). These results suggest that the LXR ligands can constitute therapeutic agents for treating atherosclerosis.
Finally, it is known that the macrophages play an important role in inflammation in particular in the pathogenesis of atherosclerosis. It has been shown that the activation of the LXRs inhibits the expression of the genes involved in inflammation at the macrophage level. (Nature Medecine, 2003; 9: 213-219). In vitro, the expression of mediators, such as nitric oxide synthase, cyclo oxygenase-2(COX-2) and interleukine-6 (IL-6) is inhibited. In vivo, the LXR agonists reduce the inflammation in a dermatite model and inhibit the expression of the genes involved in the inflammation of the aortas of atheromatous mice.
Because cholesterol homeostasis seems also to play an essential role in the operation of the central nervous system and neurodegenerative mechanisms, the ABCA1 expression has also been studied in primary neurone, astrocyte and microglia cultures isolated from the brains of rat embryos. The results of these studies show that LXR activation leads to a reduction in β amyloid secretion and as a consequence to a reduction in amyloid deposits in the brain. This work suggests that LXR activation could represent a new approach to the treatment of Alzheimer's disease (J. Biol. Chem. 2003, 275 (15): 13244-13256, J. Biol. Chem. 2003, 278 (30): 27688-27694).
LXR receptors are also involved in regulating the expression of apolipoprotein E (ApoE). This protein is heavily involved in the hepatic clearance of lipoproteins and favors the efflux of cholesterol from lipid-rich macrophages. It has been shown that the activation of LXR receptors leads to an increased expression of ApoE via an LXR response element (LXRE) located in the ApoE promoter sequence (Proc. Natl. Acad. Sci. USA 2001; 98: 507-512).
Activation of LXR receptors also favored the inverse transport of cholesterol through modulation of the expression of CETP (cholesterol ester transfer protein) which is involved in the transfer of esterified cholesterol from the HDL lipoproteins to the triglyceride-rich lipoproteins eliminated by the liver (J. Clin. Invest. 2000; 105: 513-520).
In summary, activation of LXR receptors leads to an increase in the expression of a number of genes favoring the elimination of excess cholesterol from the peripheral tissues. In the cholesterol-loaded macrophage, activation of LXR receptors increases the expression of ABCA1, ABCG1, ABCG5, ABCG8 and ApoE bringing about an increase in the efflux of cholesterol from the macrophages to the liver where it is excreted in the form of bile acids. Induction of CETP and CYP7A expression in the liver leads to an increase in hepatic clearance of cholesterol esters from the HDL lipoproteins and to catabolism of the cholesterol, respectively.
Furthermore, it has also been shown that LXR receptors play an important role in the metabolism of glucose. Treatment of diabetic rodents with an LXR agonist leads to a drastic reduction in plasma glucose levels. In particular, in the insulin resistant Zucker rat (fa/fa), LXR activation inhibits the expression of the genes involved in gluconeogenesis and most particularly of phosphoenolpyruvate carboxykinase (PEPCK) (J. Biol. Chem. 2003, 278 (2): 1131-1136). It has also been described how the treatment of mice with an LXR agonist leads to a reduction in plasma glucose levels and in production of hepatic glucose by inhibiting the enzymes that play a key role in gluconeogenesis (Diabetes, 53, suppl 1, S36-S42 February 2004)
Moreover, it has been shown that an LXR agonist increases glucose tolerance in a murine insulin resistance and obesity model (Proc. Natl. Acad. Sci. USA 2003; 100: 5419-5424). The gene expression analysis also highlights regulation of the genes involved in the metabolism of glucose in the liver:                reduction in peroxisome proliferator-activated receptor coactivator-1α (PGC-1), phosphoenol pyruvate carboxykinase (PEPCK) and glucose-6-phosphatase expression;        induction of glucokinase expression which favors the use of hepatic glucose.        
A transcriptional induction of the insulin-responsive glucose transporter (GLUT4) in the adipose tissue has also been demonstrated. These results underline the importance of LXRs in the coordination of glucose metabolism. It is also known that LXR receptors are involved in the inflammation regulation process (Nature Medecine 2003 9, 213-219).
LXR receptor activity modulator compounds are known in the prior art in particular from documents WO 03/090869, WO 03/90746, WO 03/082192 or WO 03/082802; or also from documents WO 03/043985 and WO 04/005253 which describe compounds which are PPAR receptor agonists of the benzenesulfonamide type.
In this context, there is significant interest in finding LXR receptor activity modulator compounds that could be useful in the treatment of certain pathologies such as cardiovascular disease, hypercholesterolemia, dyslipidemia, myocardial infarction, atherosclerosis, diabetes, obesity, inflammation and neurodegenerative diseases.
The present invention is specifically based on the discovery of new LXR receptor activity modulator compounds.
Thus, according to a first aspect, the present invention aims to protect, as a new industrial product, a benzenesulfonamide compound, characterized in that it is chosen from among:
i) the compounds having the formula:
in which                (H) represents a nitrogen-containing 5- or 6-membered saturated heterocyclic ring condensed with a phenyl or cyclohexyl ring, optionally substituted by a halogen, a C1-C4 alcoxy group or an N(R)2 group in which R represents the hydrogen atom or a C1-C4 alkyl group,        R1 represents:                    a chlorine atom,            a C3-C6 alkyl group, branched or cyclized,            a C2-C6 linear, branched or C3-C6 cyclized alkoxy group,            a phenoxy group, optionally substituted by a halogen,            a phenyl group, or            an aminomethyl group, optionally substituted by an acetyl or trifluoroacetyl group,                        R2 represents a hydrogen atom or a halogen, or,        R1 and R2 together form an oxygen-containing or nitrogen-containing heterocycle, optionally substituted by one or more C1-C3 alkyl groups, an acyl group or a C2-C3 perfluoroacyl group,        Y represents:                    a single bond,            a C1-C4, linear or branched or C3-C4 cyclized alkylene group, optionally substituted by a C1-C3 alkoxy group, a phenyl group, an N(R)2 group or a COOH group,            a —(CH2)n—O— group,            a —(CH2)n—S— group, or            a —(CH2)m—CO— group,n is equal to 2 or 3,m is equal to 1, 2 or 3,R represents the hydrogen atom or a C1-C4 alkyl group                        Ar represents an aromatic or heteroaromatic ring chosen from among the phenyl, naphthalenyl, tetrahydronaphthalenyl, pyridinyl or indolyl groups, optionally substituted by one or two identical or different R3, R4 substituents chosen from among a halogen, a C1-C4 alkyl, C1-C4 alkoxy, nitro, phenyl, phenoxy, trifluoromethyl, amino, hydroxy group, or a group with the formula —X—[C(R)2]p—COR5 in which:                    X represents a single bond, an oxygen atom, a sulfur atom or an NH group,            R5 represents OR or N(R)2,            R represents the hydrogen atom or a C1-C4 alkyl group,            p is equal to 0, 1 or 2;said substituents R3 and R4 also being able to form together a methylenedioxy group;ii) the pharmaceutically acceptable salts of the compounds of formula (I).                        
According to a second aspect, the invention concerns the abovementioned compounds as a pharmacologically active substance. In particular, the invention concerns the use of at least one compound of formula (I) or one of its pharmaceutically acceptable salts as an active substance for the preparation of a medicinal product intended for therapeutic use, in particular for the treatment of hypercholesterolemia, dyslipidemia, diabetes, obesity and cardiovascular disease which are the consequence of an imbalance in the serum lipoproteins. More generally, the compounds of formula I according to the invention are useful for correcting deviations in the parameters indicative of a metabolic syndrome. The compounds according to the invention are also useful as active substances in medicinal products intended for preventing or treating atherosclerosis, myocardial infarction, certain inflammatory diseases such as dermatitis, and neurodegenerative diseases such as Alzheimer's.